Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context by explaining that omitting the domain parameter returns an overview of all available domains and that locale controls language for labels/descriptions. This goes beyond what the annotations alone provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured and front-loaded: purpose first, then usage guidance, then parameters and domains, then the no-domain behavior. The domain list is somewhat long, and it partially duplicates the schema enum while being incomplete, but the structure is clear and each section earns its place for an agent needing orientation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a metadata tool with no output schema and only two optional parameters, the description gives a reasonable high-level explanation of return content, including fields, units, data types, and sources. However, it does not describe the shape or format of the returned field definitions, and the incomplete domain list creates a notable gap: an agent cannot learn from the description that socio-demographic and some macroeconomic domains are also supported.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description adds value by translating the domain enum into human-readable meanings (e.g., immobilienmarkt.berlin.wohnungen = Berlin apartment market), but the 'Available domains' list is incomplete compared to the schema enum: it omits all soziodemografie domains and makrooekonomie.preise/wirtschaft. This can mislead an agent into thinking those domains are not valid, so the description does not fully compensate for or improve on the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a clear, specific purpose: it returns field definitions for interpreting API responses, including fields, units, data types, and sources. This clearly separates it from sibling data-retrieval tools such as listings, berlin_boroughs, or macro_* tools, which return actual data rather than metadata.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly says to use this when you need to understand fields, units, data types, and sources, providing clear context for when it is appropriate. It does not explicitly name alternatives or state when not to use it, but the purpose is distinct enough from the sibling tools that an agent can infer the right situation.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.